Taking multiple ADC samples is an effective way to improve the SNR. Comparing configurations 3 and 5 in Table 2-1, the SNR is significantly improved by averaging multiple top ADC samples. The number of top ADC samples is displayed as N_TOP and the time of the first top ADC sample is t_TOP. Faster ADC sample rates allow more samples to be taken at the top of the photo pulse and improve the SNR further. This is demonstrated in configurations 5 and 7. Table 2-1 displays the time between ADC samples as t_SAMP.

Higher ADC resolutions improve the SNR to a limit. Figure 4-21 displays the effect of varying the ADC LSB size for a 260 mV amplitude pulse. The SNR drops when the ADC least significant bit (LSB) is greater than 5 mV. In this case, a 10-bit ADC with a 2 V to 3 V full-scale voltage is sufficient for maximizing SNR.

Taking multiple ADC samples of the signal before the LED is enabled is effective in systems that measure the ambient light level before the LED is enabled. This is displayed as N_BASE in Table 2-1. The benefit is shown in Figure 4-20. Because the LED is not enabled for these ADC samples, low power is consumed when taking the multiple ADC samples before the LED is enabled.

If the ADC sample rate is different from the examples in Table 2-1, take samples for the same amount of time as done in Table 2-1. For example, if a 5 μs t_SAMP is used with τ₁ and τ₂ set to 15 μs, take 40 base samples and 16 top samples.